str = 'throw new ServiceException("500","通过结算单号查找结算单DTO异常，结算单号【"+ jsonRecordPO.getSettlementNo() +"】");'

a = str.find('"')
str_a = str[str.find('"') + 1:-1]
b = str_a.find('"')
print(b)
print(str_a[0:b])

str_c = str_a[b:-1]
print(str_c)
# print(str[b[0], -01基础])